Nice install! I don't think it would pass emission tests in most of US. I have Dinan exhaust and it sounds great and very different than a stock X5 exhaust. For racing or lots of noise I have electric cutouts that can be opened as much and as little as desired. No drone using either. Just an option for others considering exhaust mods. You may be getting a small gain in HP/TQ using headers especially if they are equal length. In the good ol' days we installed headers so we could remove them from the collector, drop the exhaust down to connect to the bottom bolt only, so we had open headers.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas